Methods and Positions for Branding of Pla Duk Dan (Clan'as batrachus Linn.)

Abstract

Two experiments were conducted in order to get an appropriate technique for branding Pla Duk Dan (Clarias batrachus Linn.) with the criteria based on growth, survival and percentage of fish showing mark identification. The first experiment, two types of instruments were used, electrical hot-wire branding instrument developed by Moav et al. (1960 b) and cold branding instrument to compare their effectiveness. The fish were branded about midway of body depth at 2 positions1,~ ofb ody length from head and 31 from tail. The results showed that branding with these instruments at two different positions had no effect on mortality of the fish. Fish branded by electrical hot-wire at the latter position showed longest identification period (90% identified fish after 6 weeks of branding). 1 The hot-wire branding instrument should therefore be used for branding at the position o f 3 of body length from tail. The second experiment was made to evaluate the effect of hot-wire branding on growth and survival rates of Pla Duk Dan and the period of such branding mark identification. Pla Duk Dan of 25.79 5 86.5 cm long, 119.51 2 86.21 g. in body weight were branded by using electrical hot-wire branding instrument at about midway of body depth and at the position1~ obf ody length from tail. Sixty, 120,180 and 240 days after branding revealed that growth and survival rates of the branded fish were as the same as the controlled group. After 180 days of branding, 93.87% of the branded fish still showed mark identification, and at 240 days after branding 69.38% fish still showed those mark.